Gob
The mouth, usually with the implication of mouth-as-noise-source. 'Shut your gob' = be quiet. 'Have a gob on him' = have a mouth on him, talk too much. Distinct from 'bake' (more Ulster) but functionally similar.
Etymology
From Irish 'gob' meaning beak or pointed mouth (of a bird, often used metaphorically for a human mouth in critical register). The Irish form reaches deeper, with cognates across Celtic languages. Hiberno-English took the word with the slightly-rude implication intact - calling someone's mouth their gob is more direct than 'mouth' and less polite, in the same way that 'bake' or 'gob' substitute for 'face' or 'mouth' in casual speech.
In a sentence
"Will you shut your gob a minute and let me finish what I was saying?"
Historical notes
Gob is one of the Irish-derived Hiberno-English words that has settled into general English so completely the origin is invisible. Standard British English uses 'gob' for mouth in informal speech without flagging it as Irish; American 'gobsmacked' (= astonished, as if hit in the mouth) is the same root. Hiberno-English keeps the word fully active and uses it across compounds: 'gobby' (= mouthy), 'gobshite' (= a person who talks too much, often offensive), 'big gob on him' (= talks loudly).
Sources
- Foclóir Gaeilge-Béarla (Ó Dónaill), entry gob. · dictionary
- Oxford English Dictionary, entry gob n. (mouth). · dictionary