Where does “trawst” come from?

trawst (Welsh) comes from Middle Welsh trawst, from Proto-Brythonic *trọstr, from Latin transtrum, from Latin trāns, from Latin Padus, from Lepontic Bodincus, from Proto-Indo-European bʰudʰmḗn, from Proto-Indo-European dʰewbʰ- — smoke; mist, haze.

trawst (Welsh): beam, crossbeam, rafter

Definitions

beam, crossbeam, rafter

Ancestry of “trawst”, step by step

Step	Language	Word	Meaning
1	Middle Welsh	trawst	—
2	Proto-Brythonic	*trọstr	—
3	Latin	transtrum	crossbeam, transom; thwart of a vessel
4	Latin	trāns	across, beyond
5	Latin	Padus	the River Po
6	Lepontic	Bodincus	—
7	Proto-Indo-European	bʰudʰmḗn	bottom
8	Proto-Indo-European	dʰewbʰ-	deep
9	Proto-Indo-European	dʰewh₂-	smoke; mist, haze

Every word from Proto-Indo-European dʰewh₂- →Every word from Proto-Indo-European dʰewbʰ- →Every word from Proto-Indo-European bʰudʰmḗn →