wood

so far I could find, the PIE root for "wood" should be *keld-
The reflexes of this root can be found in German holz", Russian
"koloda", Greek "klaéin", Latin *cellere > pre-cellere

The rom. word for "wood" is "lemn" and it is supposed to come from latin
"lignum".
Indeed I do not find any PIE root which directly point to "wood" and
having the form "*len-" but there is an another root which show some
cimilar semantic transformation in other languages.I speak about PIE
*lento-s = flexible
Of course the semantic development from "flexible" to wood may be
strange but let see what we have in actual languages:

German: Linde = this is a tree, English "linden"
Russian : lut
Lithuanian: lenta= a table made from linden

It seems to me that, even if there are semantically cognates in other
languages, the Rom. "lemn" could not derive phonetically from *lento-s
because the "nt" remain "nt" in Rom. without transformation. And there
is the word " alint, alinta"="to caress; to pamper; to fondle" which
derive from the PIE root "lento-s" . The word has cognates in german:
"lindern"=soft, gentle, mild but is given by DEX as beeing from Latin
*allentare a supposed derivative of Latin "lentus".

The question for me here is, which is the etymology of Latin word
"lignum"?