Мнение Wiktionary:
Со словом folk не связано никак, оно из другой совсем формы происходит:
Сяргей Леанідавіч, мне нравятся такие арументы!
Ultimately from Proto-Germanic *walhaz. Exact donor language cannot be specified;
А мнений об этимологии бывает не одно. Вот, например, 2 мнения Wiktionary насчёт этимологии английского галлицизма
foule:
Etymology 1
Inherited from Middle French foule (“group of men, people collectively”), alteration (due to Middle French foule (“act of treading”)) of Old French foulc (“people, multitude, crowd, troop”), from Early Medieval Latin fulcus, from Frankish *folc, *fulc (“crowd, multitude, people”), from Proto-Germanic *fulką (“collection or class of people, multitude; host of warriors”), perhaps from Proto-Indo-European *pleh₁- (“to fill”). Cognate with Old High German folc (“people collectively, nation”), Old English folc (“common people, troop, multitude”). More at folk.
For the loss of c after l, compare Old French mareschal, seneschal, etc.
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Etymology 2
From Middle French foule (“the act of milling clothes or hats”) and fouler (“to trample, mill, fordo, mistreat”), from Old French foler (“to crush, act wickedly”), from Latin fullō (“to trample, to full”). More at full.
https://en.wiktionary.org/wiki/foule#French
Точно неуказуемая этимология вольков тоже вполне себе способна прирасти
