to search for lice; thus chat-up n., a search for lice.
|Gippsland Times (Vic.) 27 May 3: One of the forced pastimes of the soldier is ‘chatting for chats’.|
|Lingo of No Man’s Lnd 20: CHATTING Name applied to the indiscriminate hunt for petit friends called ‘cooties,’ ‘trouser-rabbits,’ etc.|
|Digger Dialects 16: chat (vb.) — To examine clothing in order to remove lice.|
|N&Q 12 Ser. IX 424: Chat-Up. A spell of killing vermin.|
|(con. WWI) Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: chat. The vermin that infested clothing, blankets & Dug-outs. To search clothing for Chats.|
|Behind Bamboo 395/2: Chat, (to), to delouse. Chat happy, weary of delousing clothes, etc.|