coif / quaff are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
coif: (noun) a skullcap worn by nuns under a veil or by soldiers under a hood of mail or formerly by British sergeants-at-law. (verb) cover with a coif.
quaff: (noun) a hearty draft.
coif: NA
quaff: NA
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)