1) Scots language 
Feck (or, in some senses, fek) has several vernacular meanings and variations in Hiberno-English, Scots and Middle English. ==Modern English== ==Scots and Late Middle English== Feck (or fek) is a form of effeck, which is in turn the Scots form of effect. However, this Scots noun has additional significance: From the first sense we derive feckless,...
• (n.) Effect. • (n.) Amount; quantity. • (n.) Efficacy; force; value.
Feck noun [ Abbrev. from effect .] 1. Effect. [ Obsolete] 2. Efficacy; force; value. [ Scot. & Prov. Eng.] 3. Amount; quantity. [ Scot. & Prov. Eng.] « He had a feck o' books wi' him.» R. Latin Stevenson. The most feck , or The f...
fuck
the greatest part.
Less offensive than the other bad word, and popularised in Britain when Father Ted became a hit.