hardly (adv.)

c. 1200, "in a hard manner, with great exertion or effort," from Old English heardlice "sternly, severely, harshly; bravely; excessively" (see hard (adj.) + -ly (2)). Hence "assuredly, certainly" (early 14c.). Main modern sense of "barely, just" (1540s) reverses this, via the intermediate meaning "not easily, with trouble" (early 15c.). Formerly with superficial negative (not hardly). Similar formation in Old Saxon hardliko, German härtlich, Old Danish haardelig.

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Definitions of hardly from WordNet

hardly (adv.)
only a very short time before; "would have scarce arrived before she would have found some excuse to leave"- W.B.Yeats;
we hardly knew them
Synonyms: barely / just / scarcely / scarce
hardly (adv.)
almost not;
I can hardly hear what she is saying
he hardly ever goes fishing
Synonyms: scarcely / barely / scarce
hardly (adv.)
slowly and with difficulty;
he was so dizzy he could hardly stand up straight
Synonyms: hard