Green’s Dictionary of Slang

whistle v.

[it makes a ‘noise’]

to smell unpleasantly.

[UK]Auden & Isherwood Dog beneath Skin (1946) 113: Wot wouldn’t I give fer a bath? Cor! I don’t ’alf whistle!
[UK]Barltrop & Wolveridge Muvver Tongue 68: A strong smell is credited with extra impact on the senses: ‘Don’t half hum’ or ‘Doesn’t half whistle.’.

SE in slang uses

In phrases

whistle in the cage (v.) [fig. use of SE whistle +cage n. (8); the note appears in later edns. of Scott (1815)]

for a villain, on being arrested, to betray his accomplices.

[Scot](con. 18C) W. Scott Guy Mannering (1999) 149: [Note] To sing out, or whistle in the cage, is when a rogue, being apprehended, peaches against his comrades [F&H].
whistle through one’s arse (v.)

(Aus.) to speak sincerely but speciously.

[Aus]B. Robinson Aussie Bull 42: These well-meaning ‘ostriches’ seem to bury their heads in theoretical sands and try to whistle through their learned rectums.
you ain’t just whistling (Dixie) (also you doggone whistling)

(US) you really mean what you’re saying, you’re not just being flippant.

[US]E. Anderson Thieves Like Us (1999) 17: You doggone whistling.
[US] ‘Whitman College Sl.’ in AS XVIII:2 Apr. 155/1: you ain’t just a-whistlin’ dixie; you ain’t just beatin’ your gums [...] Terms denoting satisfaction and agreement.
[US]L. Uris Battle Cry (1964) 135: You ain’t just awhistling through your buckteeth.
[US]N. Spinrad Bug Jack Barron 96: ‘You ain’t just whistling Dixie,’ Barron interrupted. ‘A million’s a nice round number.’.
[US]H. Harrison Bill [...] on the Planet of Robot Slaves (1991) 118: You ain’t just whistling Dixie, pardner.