Old English feawe (plural; contracted to fea) "not many, a small number; seldom, even a little," from Proto-Germanic *fawaz (source also of Old Saxon fa, Old Frisian fe, Old High German fao, Old Norse far, Danish faa), from PIE root *pau- (1) "few, little."
Always plural in Old English, according to OED "on the analogy of the adverbial fela," meaning "many." Phrase few and far between attested from 1660s. Unusual ironic use in quite a few "many" (1854), earlier a good few (1803).
There is likewise another dialectical use of the word few among them [i.e. "the Northern Counties"], seemingly tending to its total overthrow; for they are bold enough to say--"a good few," meaning a good many. [Samuel Pegge, "Anecdotes of the English Language," London, 1803]