An archaic or dialectal form meaning to frighten or to become afraid; sometimes used in older English to describe shaking with fear.
From Old English galan meaning 'to sing' or possibly from a Germanic root related to fear or trembling; the exact evolution is debated among linguists.
This word is almost entirely extinct in modern English, but it survives in some Scottish and Northern English dialects, and you can see its traces in the word 'ghastly,' which originally meant something like 'fear-inducing.'
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