Green’s Dictionary of Slang

a whore, a promiscuous woman.

1607		Shakespeare Antony and Cleopatra III xi: You have been a boggler ever.
1822		R. Nares Gloss. (1888) I 90: boggler. One who boggles, but in the following passage [see 1606 above] a vicious woman, one who starts from the right path [...] Johnson in his Dict. explains it as a doubter, a timorous man; but it is evidently addressed not to Thyreus but to Cleopatra.