means Fitting closely and comfortably, warm and sheltered, or tight enough to leave little room to spare.

from Snug surfaced in English in the late 16th century as a nautical word, describing a ship that was trim, well-protected, and ready for bad weather — compact and shipshape. It's likely borrowed from a Low German or Scandinavian source (compare Old Norse 'snøggr,' meaning short or close-cut). Only later did it drift ashore to mean warmly tucked away, giving us the snug little room and the phrase 'snug as a bug in a rug.'