A hug that wraps someone in warmth and security.
A hug that wraps someone in warmth and security — and, in its other everyday sense, a little cupboard or snug nook for tucking things safely away.
What lifts it above an ordinary hug is the sense of sheltering someone — the same word, after all, names a small safe space. Compared with German Geborgenheit (an abstract state of security and shelter), cwtch is the concrete act — an embrace, and secondarily a physical nook — rather than the state. More bodily and enclosing than general warmth or affection.
No single literal gloss — the word fuses “hug/cuddle” with “cubbyhole / safe place,” so to cwtch is to make a safe little place around someone with your arms.
A loanword (no recognized Celtic cognates); the leading hypothesis is from Welsh cwts/cwtsh, ultimately from Old French couche “a resting/hiding place” (the source of English couch), entering Welsh around the Norman invasion.
Long colloquial in South Wales; the “cubbyhole” sense is well attested, and the “hug” sense rose to national prominence in the 20th–21st centuries. Added to the Concise Oxford English Dictionary in 2005; voted Wales's favorite word in 2007.
Genuinely attested (OED-recorded), not merely a listicle word. Only the etymology is uncertain (loanword status accepted; the exact Old French route is a leading hypothesis). Spelling varies: cwtch / cwtsh / cwts.