The original Frisian coat of arms had water-lily leaves ("pompebladen") in it.
Wiki "Flag of Friesland" has no answer:
The Frisian flag, is the official flag of the Dutch province of Friesland. It consists of four blue and three white diagonal stripes; in the white stripes are a total of seven red pompeblêden, stylised heart-shaped leaves of yellow water-lily.
The seven red pompeblêden are a reference to the Frisian "sea countries" in the Middle Ages: independent regions along the coast from Alkmaar to the Weser who were allied against the Vikings. There were never precisely seven distinct rulers, but the number seven probably has the connotation "many."
Since the 11th century a coat of arms with pompeblêdden is known. Evidence for this lies within verses of the Gudrunlied. Round 1200 Scandinavian coats of arms reveal many traces of water-lilies and hearts, found often in combination with images of lions.
15th century books on heraldry show that two armorial bearings were derived from the early ones: a coat of arms showing lions and seven pompeblêdden transformed into little blocks, the other being the arms with the seven now known lilies on stripes.
~ ~ ~ ~ ~ ~
The following fragment of Oera Linda Book could explain why 'pomp'-leaves had a very important meaning to the old Frisians:
[OLB p.064/11] ca. 1630 BC; KÀLTA's speech:
SVNUM ÀND TOGHATRUM FRYA.S.
I WÉT WEL THÀT WI INNA LERSTE TÍD FÚL LEK ÀND BREK LÉDEN HÀVE.
THRVCHDAM THA STJURAR NAVT LÔNGER KVME VMB.VS SKRIF.FILT TO VRSELLA.
ANDA ÔRA SYDE THÉRE SKELDA HWÉR HJA TOMET THA FÉRT FON ALLE SÉA HÀVE
THÉR MÁKATH HJA HJVD.DÉGON SKRIF.FILT FON POMPA.BLÉDAR
THÉRMITH SPARATH HJA LINNENT UT ÀND KÀNATH HJA VS WEL MISTE.
NÉIDAM THÀT SKRIF.FILT MÁKJA. NV ALTI VS GRÁTESTE BIDRIV WÉST.IS.
SÁ HETH THJU MODER WILT THAT MÀN.ET VS LÉRA SKOLDE.
Improved English translation (as Sandbach had too many errors):
Sons and daughters of Frya,
you know well that we in last times have suffered much loss and misery
because the sailors no longer come to buy our writing-felt
On the other side of the Scheldt, where they almost have the trade of all seas,
there they nowadays make writing-felt of water-lily leaves.
With that they save linen and no longer need us (lit.: can they miss us).
Because the making of writing-felt has always been our greatest trade,
the mother willed that one should teach us
So first "SKRIF-FILT" was used, made of "LINNENT", later paper made of "POMPA-BLÉDAR".
In the OLB, a word for 'paper' is used only once, as "PAMPÍER" [letter Hidde (1256 AD) line 11]:
VMBE HJA NAVT TO VRLYSA HÀB IK RA VP WRLANDISK PAMPÍER VVRSKRÉVEN.
In order not to lose them, I copied them on foreign paper. (Sandbach)
The word "paper" in modern European languages never has a "M" before the second "P" (or "B"):
paber - Estonian
páipéar - Irish
papel - Spanish, Portuguese
paper - English
папир - Servian
папера - White-Russian
paperi - Finnish
papier - Dutch, Frisian, German, French, Polish, Slovakian
papir - Danish, Norwegian, Kroatian, Ukrainian (папір)
papír - Hungarian, Czech
papirja - Slovenian
papīrs - Latvian
papper - Swedish
pappír - Icelandic
papur - Welsch
popierius - Lithuanian
But in various Frisian texts, from before and after publication of the OLB, varieties with an "M" were used:
pompier: 1807, 1821, 1834, 1864, 1867, 1874, 1880, 1885, 1889, 1895, 1896 (2x), 1901, 1902, 1913, 1920, 1923, 1935, 1946
pampier: 1816, 1824, 1882
pumpier: 1855, 1871
1807 Nim dizze rijgels oon, nim oon dit lyts pompier. E. NAUTA, rymbrief, (1)
1816 De hudde Wijn dij hie wat proesd / En onder de Pampieren poesd. P.G. DEKETH, pijtter, strofenr. 46
1821 (ca.) Yn schier pompier berolle. E. HALB, freun
1824 Ho earm binne wij oon marcken, omme for-schaette, heegjende in leegjende luwden ... op it pampier mielje to kinnen. R. POSTHUMUS, prieuwcke, XIII
1834 Doe grou pompier: dat spielde er eak al gou wer ôaf. E. HALB, lapekoer III, 402
1855 Set naut dalik ol huet dy în 't sin sciet uppa 't pumpier. H. SYTSTRA, Iduna, 140
1864 De diakens ... founen okkersneins f 4000 oan Russisk pompier în 'e budel. W. DYKSTRA, nysbode, nr. 3, 3
1867 Tsjinwirdich barre de boeren al gau ris pompierkes for hiar bûter, mar destiids faek goudjild. W. DYKSTRA, wever, 20
1871 Ik (jow) jou alles în biwar end jy jowe my up libben end dead der en lîts pumpierke fen în 't bywêsen fen jou wîf end soan. G. COLMJON, Sw., 54
1874 Hy (wier) mei falske pompieren ... wer în 't lând komd. P. BLEEKSMA, F.m.n., 159
1880 Om it noazblieden, as dat al to stjelpich giet, to stuitsjen, moat me grou pompier kôgje ef in string keulsce side om 'e hals dwaen. H.G. v.d. VEEN, wrald, 48
1882 Pieter (is) oan de doar ... in greate rol pampier ûnder de earm. P.J. TROELSTRA, wiersizzery, (6)
1885 Yn forskate hûzen hinget in great pompier efter in glês mei in swarte list er om hinne ... op dat pompier stiet ... in forklearringe. M.P. TROELSTRA, Sw., 59
1889 Bûrman naem syn boekje op, der der in pompierke út krige hie, in Russiske coupon. J.D. BAARDA, forsin, 47
1895 De Eastenrykse pompieren, dy mochten wy wol fen 'e hân dwaen en keapje er wer Spaenske foar. T.W. SYTSTRA, F.m.n., 152
1896 It rint yn 'e pompieren. W. DYKSTRA, volksl. II, 388
1896 Dy faem is op skien pompier - 'heeft geen vrijer aan de hand'. W. DYKSTRA, volksl. II, 311
1901 For in tachtich goune silverjild (hie) (er) tsjin pompier wiksele. T.G. v.d. MEULEN, Sw., 94
1902 In oaren-ien, oars ek wol yn steat om moai dúdlik syn tinzen op 't pompier to bringen, skreau djarp for doarp. J. f.'e GAESTMAR, F.m.n., 187
1913 Ik hab jimme gâns to skriuwen, mar ik hab soks net wollen mei pompier en inket. E.B. FOLKERTSMA, Y.ú.e.t., 72
1920 De bank hoegde dos net safolle munt yn kas to hawwen as der pompier yn omrin wier. P.T. ZWART, Heit., 36
1923 Der wirdt yn dizze wrâld nearne sa folle liichd as op 't pompier. J.P. WIERSMA, arbeiders-jongfolk, 7
1935 Hjir lizze noch wol in pear pompierkes op 't taffeltsje. S. BOUMA, wolken, 6
1946 Men (sit) efter it swarte pompier by in lyts ljochtsje mei it daei om to kliemen. W. KOK, koarstekoeke, 80
(Note that E. Halbertsma (1821, 1834) spelled: "pompier")
If the OLB story is right it would explain two things:
1) why the Frisian flag is made up of 'pomp'-leaves
2) why the most common old-Frisian spelling of paper was "pompier"
If the OLB was created in the 19th century, its author(s) must have been an etymology fanatic. The etymology of "pompier" seems obvious, yet nothing is said about it in the OLB, and the only time the word for paper is used, it is spelled as "pampíer", while "pompier" would be more pure.
I think this could be an important clue.