Glib

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late 16th century (also in the sense ‘smooth, unimpeded’): ultimately of Germanic origin; related to Dutch ‘slippery’ and German glibberig ‘slimy’.

wiktionary

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A shortening of either English glibbery(“slippery”) or its source, Low German glibberig, glibberich(“slippery”) / Dutch glibberig(“slippery”).

From Irish glib.

Compare Old English and dialect lib to castrate, geld, Danish dialect live, Low German and Old Dutch lubben.

etymonline

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glib (adj.)

1590s, "smooth and slippery," a dialect word, possibly a shortening of obsolete glibbery "slippery," which is perhaps from Low German glibberig "smooth, slippery," from Middle Low German glibberich, from or related to glibber "jelly," all part of the Germanic group of gl- words for "smooth, shining, joyful," from PIE root *ghel- (2) "to shine." Of words, speakers, etc., from c. 1600. Related: Glibly; glibness.