In notes from the 1950s Tolkien said the word besain was a title for noble Elf ladies as the provider of lembas, the equivalent of (and probably adapted from) Q. massánië, literally “bread giver [giving]” (PM/404). It was likely coined based on the historical developments of this name: *mbassānye > (m)bessenı̯ > bessein > besain. Christopher Tolkien noted that his father wrote oneth above -ain, indicating an alternate form, which Christopher Tolkien wrote as *besoneth (PM/405). However, I think it is likelier the alternate would be *basoneth = S. bas “bread” + oneth “*giver [f.]”, because in this alternate form there would be no reason for the initial element bas- to undergo i-affection.