To make something hard or callous; to harden or make insensitive.
From en- + callow (which means inexperienced or immature, from Old English ceale, meaning bald or bare). The prefix 'en-' inverted the meaning toward hardening rather than softening.
Wait—'callow' means young and inexperienced, so 'encallow' meaning to harden is backwards in an interesting way. It's like saying 'make youthful' when you mean 'make hard'—a linguistic quirk that makes you do a double-take!
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