'cheer' originates from Old French, specifically the word 'chiere' (also written 'chere'), where 'chiere' meant 'face, countenance' and by extension 'mood' or 'expression'.

'cheer' changed from Middle English 'chere' (meaning 'face, expression, mood') and through later usage developed senses of 'mood' and 'encouragement'; the exclamation 'cheers' as a toast developed later in modern English.

Initially it meant 'face, expression,' but over time it evolved into meanings related to 'mood' and 'encouragement,' and eventually into the modern interjection senses 'toasting,' 'thanks,' and informal 'goodbye.'