Green’s Dictionary of Slang

to feign sleep or (Aus.) to feign unconsciousness.

1896		‘Frederick Benton Williams’ (H.E. Hamblen) On Many Seas 357: So we hunted him over for other wounds, but, not finding any, came to the conclusion that he was foxing, and I gave him a kick in the ribs and ordered him to get up.
1976		D. Ireland Glass Canoe (1982) 62: ‘Is he alive?’ ‘He’s foxing.’.