Plural of hallo; multiple shouts or greetings of 'hallo,' or the act of hallooing multiple times.
From 'hallo' plus the English plural suffix '-es' (used because 'hallo' ends in 'o'). Represents multiple instances of the interjection or the action of shouting hallo.
Words ending in 'o' get 'es' plurals—potatoes, tomatoes, heroes—which is why we don't say 'hallos' but 'halloes,' following a quirk of English that survives from Old English rules about vowel endings.
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