Boggle

google

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late 16th century: probably of dialect origin and related to bogle and bogey2.

wiktionary

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Variation or derivation of bogle, possibly cognate with bug.

boggle (plural boggles)

etymonline

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boggle (v.)

1590s, "to start with fright (as a startled horse does), shy, take alarm," from Middle English bugge "specter" (among other things, supposed to scare horses at night); see bug (n.); also compare bogey (n.1), boggart. The meaning " hesitate, stop as if afraid to proceed in fear of unforeseen difficulties" is from 1630s; that of "confound, cause to hesitate" is from 1640s. As a noun from 1650s. Related: Boggled; boggling; boggler (from c. 1600 as "one who hesitates").