I Americans serving in France were said to be known as les sommobiches (see also
son of a bitch). But the earliest French use of the word (12c.) is as the name of a people apparently in southern Gaul (which led to the now-doubtful, on phonetic grounds, theory that the word comes from Visigoth). Sp. bigote "mustache" also has been proposed as a source, though the sense is not adequately explained. The earliest English sense is of "religious hypocrite," especially a female one, and may have been influenced by
beguine. Sense extended 1680s to other than religious opinions.