The name is related to Welsh helyg(en) and Latin salix.
[1] The etymology and kennings unambiguously confirm the meaning "willow" for this letter name.
The Morann mic Moín kenning is a reference to the sallow grey appearance of the bark of this tree, while the kennings referencing bees and honey are due to its being commonly pollinated by bees.
[3] While medieval and modern neopagan arboreal glosses (i.e. tree names) for the Ogham have been widely popularised (even for feda whose names do not translate as trees), the Old Irish In Lebor Ogaim (the Ogam Tract) also lists many other word values classified by type (e.g. birds, occupations, companies) for each fid.
fili) or poets of this period learned around one hundred and fifty variants of Ogham during their training, including these word-list forms.