1844, American English, short for chaparejos, from Mexican Spanish chaparreras, overalls worn to protect from chaparro (see chaparral).

"jaws, cheeks," from chap (n.), 1550s, of unknown origin. Hence, chap-fallen (1590s).

guys

The acronym should come first as it’s more widely known than the full name.

leather pants joined together by a belt or laces, which tend to have flared out flaps. Chaps are worn over pants.

This stands for Clearing House Automated Payment System. An electronic payment system that guarantees same day payment.

Clearing House Automated Payments System. An electronic transfer system for sending real-time gross settlement same-day value payments in sterling from bank to bank.

(Clearing House Automated Payment System). Allows electronic payments to be made and cleared the same day. Banks can charge up to £35 per transfer.

Chaps are leg protectors for a bird, primarily used when hunting squirrels as the squirrel teeth can severely damage a bird's leg or toe. Choanal slit

Stands for Clearing House Automated Payment Service - allows you to make a same day withdrawal from your account.

Clearing House Automated Payment System

Acronym for Clearing House Automated Payment System. Assuming they are transferred within time, payments will clear into a designated account the same business day.

See BACS 

(British)a method of same-day banking transfer.