He disappeared on our left as before, and, after a few moments' delay, remerged and took his course down into the swamp again.
1630s, "to plunge or sink in," from Latin mergere "to dip, dip in, immerse, plunge," probably rhotacized from *mezgo, from PIE *mezg- "to dip, plunge" (cf. Sanskrit majjati "dives under," Lithuanian mazgoju "to wash"). Legal sense of "absorb an estate, contract, etc. into another" is from 1726. Related: Merged; merging. As a noun, from 1805.