Abarim Publications' online Biblical Hebrew Dictionary
Of the unused root אחל ('hl), BDB Theological Dictionary says "existence and meaning dubious". But the Bible contains one word and one name that seem to have come from it, namely the name Ahlai and the petitionary outcry אחלה ('ahlah), usually translated with "ah that!" (Psalm 119:5 and 2 Kings 5:3).
BDB suggests that this word may in fact be a construct of the more common cry אח (ah), indeed meaning Ah!, and the word לו (lu), a particle denoting potentiality and desire: if only, I wish, etcetera.