Etymology
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ha-ha 
also haha, used of laughter since ancient times; Old English ha ha. Also in Greek (ha ha, in Euripides, Aristophanes), Latin (hahae). A different attempt at representation in English is py-hy (1580s). Sometimes interchanged with ah and expressing surprise, distress, etc. A ha-ha (1712), from French, was "an obstacle interrupting one's way sharply and disagreeably;" so called because it "surprizes ... and makes one cry Ah! Ah!" [Alexander Le Blond, "The Theory and Practice of Gardening," 1712].
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a-ha (interj.)

also aha, exclamation of surprise or delighted discovery, late 14c., from ah + ha.

This seely widewe and hire doughtres two ... cryden out "harrow!" and "weloway! A ha! þe fox!" and after him they ran [Chaucer]
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ha (interj.)
natural expression of surprise, distress, etc.; early 14c., found in most European languages (including Latin and Old French) but not in Old English (which did, however, have ha-ha).
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yoo-hoo (interj.)
exclamation to call attention, by 1913.
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boo-hoo (interj.)
also boohoo, 1520s, originally of laughter or noisy weeping (now only of weeping); see boo. As a verb from 1838.
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he-he 

imitative of laughter, Old English.

Ha ha and he he getacniað hlehter on leden and on englisc. [Ælfric, "Grammar," c. 1000]
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aha (interj.)

expression of surprise or delighted discovery, late 14c., from ah + ha.

This seely widewe and hire doughtres two ... cryden out "harrow!" and "weloway! A ha! þe fox!" and after him they ran [Chaucer]
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alas (interj.)

mid-13c., from Old French ha, las (later French hélas), from ha "ah" + las "unfortunate," originally "tired, weary," from Latin lassus "weary" (from PIE root *‌‌lē- "to let go, slacken"). At first an expression of weariness rather than woe.

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Hanoi 
city in northern Vietnam, from Vietnamese Hà Nôi, literally "River Inside," from "river" + nôi "inside." So called in reference to its situation in a bend of the Red River. Known 18c. as Dong Kinh "Eastern Capital," which was corrupted by Europeans into Tonkin, Tonquin, and that name was used in the French colonial period to refer to the entire region and extended to the gulf to the east.
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