Ah

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Middle English: from Old French.

wiktionary

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mid-1400s Old Frankish (replacing English la).

ah(Singapore,Singlish,Malaysia)

etymonline

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ah (interj.)

mid-15c., an expression of surprise, delight, disgust, or pain in nearly all Indo-European languages, but not found in Old English (where the equivalent expression was la!), so perhaps from Old French a "ah!, oh! woe!"