'thick-slice' originates from Modern English as a compound of the adjective 'thick' and the verb 'slice'. 'thick' goes back to Old English 'þicce' meaning 'thick'; 'slice' entered English via Middle English from Old French/Frankish or a related Germanic source meaning 'to cut'.

'thick' developed from Old English 'þicce' with the meaning 'thick', while 'slice' appeared in Middle English as 'slicen' (from Old French/Frankish or a Germanic root) meaning 'to cut a piece'. In Modern English the words combined into the compound verb/noun/ adjective form (e.g. 'thick-slice', 'thick-sliced').

Initially the elements meant 'thick' + 'to cut'; over time the compound came to be used specifically for cutting or describing food that has been cut into noticeably thick slices, and it is commonly used as an adjectival descriptor ('thick-sliced bacon').