Meaning

noun a conspicuous disparity or difference as between two figures

noun an open or empty space in or between things

noun a narrow opening

originInherited from Middle English gap /gappe, from Old Norse gap (“an empty space, gap, chasm”), from gapa (“to gape, scream”), from Proto-Germanic *gapōną, from Proto-Indo-European *ǵʰeh₂- (“to open wide, gape”). Related to Danish gab (“an expanse, space, gap”), Old English ġeap (“open space, expanse”). Doublet of gape.

Etymology from Wiktionary, CC BY-SA 3.0