Bashful

google

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late 15th century: from obsolete bash ‘make or become abashed’ (from abash) + -ful.

wiktionary

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Apheresis of abashed +‎ -ful(“full of”).

etymonline

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bashful (adj.)

1540s, "excessively modest, shy and sheepish," with -ful + baishen "to be filled with consternation or dismay" (mid-14c.), from Old French baissier "bring down, humiliate" (see abash). An unusual case of this suffix attached to a verbal stem in the passive sense. Related: Bashfully; bashfulness (1530s).