פֿון
'of, from'

ETYMOLOGY

[The use of פֿון in comparisons appears to be a calque of Polish od, e.g., גרעסער פֿון מיר większy ode mnie 'bigger than me']
{Why /u/? BMZ gives no MHG citations with "vun", Lexer gives two, one is Michael Beheim's Buch von den Wienern, written by Beheim around 1465 in a literary language that is "Swabian East Franconian with numerous Bavarian-Austrian forms." Perhaps an indication of the Bohemian German that Jews once learned?}
Wenker's Sprachatlas map №8 "von" shows two main areas with "vun", a larger one south of Frankfurt am Main (incl. Wiesbaden, Mainz and Mannheim), and another in Upper Saxon in area west and south of Leipzig. The first area is most suggestive as an area of old Jewish settlement.
Other examples where Yiddish has /u/ for NHG /o/? וווּ
DW¹ notes use of NHG von with the accusative in "derber norddeutscher umgangssprache", e.g. "er ist vons land, vons erste regiment", which is reminiscent of Yiddish פֿון דאָס נײַ.]
OS fan, fana, Dutch van, OHG fana, fona, MHG vone, von, van, NHG von; from PGmc ✱fanē (prep.) 'from' < ✱h₂po-neh₁ (DRV), derived from the element ✱fa, which continues the allative case ✱h₂p-ó of the PIE root noun ✱h₂ep-, with the ablative suffix ✱-nē < ✱-neh₁. Related to ✱aba (see אָפּ־ 2), which it displaced as a preposition.
Related: Lithuanian pa- (prefix), Old Church Slavonic po, Russian по, 'after, on, by, at'

WESTERN

Old Literary Yiddish (ca. 1100-1800)

בֿון

{Cambridge Codex, ca. 1382; Eli Katz (1963) 80ff.}
Approximate pronunciation: /vun/ or /von/
Notable that initial consonant appears voiced /v/, as widely in MHG von.

fun, fən {Schnitzler, Prager Judendeutsch, 23}

Wer brengt zu mir, trogt fün mir.

Alsace (France)

fʊn, fon {ALSACE, Grussenheim, Zuckerman 1969, 44}

di grɛnc ɩš vajd fʌn dɔu די גרענץ איז ווײַט פֿון דאָ {ALSACE, 47075 Mulhouse 007-040}

Switzerland

fon, fom, fum {SWITZERLAND, Fleischer 2005}

füm keniglichen Hof פֿון קעניגלעכן הויף {BURGENLAND, Stalek 1926: 269}

Oyberland (West Transcarpathian)

fün {WTCP, Budapest, Hutterer 1965: 124, 141}

fyn {WTCP, Dunajská Streda, 47179}
- fyɱ vy zɛnən zɩ פֿון וווּ זענען זי 'where are you from?'
- ɔbα ɔx vaːs nɩks fym véːm, -ən אָבער איך ווייס ניט פֿון וועם, ־ען

fyn {WTCP, Vác, 47197}
- fyːn hoːr פֿון האָר
- fyŋ gʲyːt leˑdər פֿון גוט לעדער

fyn {WTCP, Berettyó-Újfalu, 47212}
- ixɔ gʲəlajnt fỳnɛm איך האָב געלייענט פֿון אים 'I've read about him'

CENTRAL

fįn {Hutterer 1965: 141}

Unterland (East Transcarpathian)

fɩn dɩ šmuəle šiəx פֿון די שמאָלע שיך {ETCP, Sîg Felső Szek, 47223}

dɩ grejnəc ɩz vaˑt fɩn du די גרענעץ איז ווײַט פֿון דאָ {ETCP, Bistriţa, 47241}

• fon viˑ bɪstə פֿון וווּ ביסטו
• fon vanən zɛnt iˑr פֿון וואַנען זענט איר

fɩn gʎuɩs פֿון גלאָז {POLAND, Wolbrom, 50196}
- fɩ̃ gít léːdɛ פֿון גוט לעדער
- fɩ̃ ziˑx alʲãj פֿון זיך אַליין

fᵻn varʃ'ɛ פֿון וואַרשע {Warsaw, Geller 2001: 207}

NORTHEASTERN

עס איז ניטאָ קיין מאָל די פּרעפּאָזיציע אויס, און אין דעם פֿאַל פֿאַלט עס צונויף מיטן סטאַנדאַרד־לשון: געמאַכט פֿון זײַד, געמאַכט חוזק פֿון אים, הויזן פֿון פּראָסטע סחורה

Lithuania

fun {LITHUANIA, Vilnius, 54257}