嘗て。

かつて。That's a new one. I've been encountering lots and lots of vocab that's new to me, but you'd think, in studying 短歌 (tanka) and 昔話 (folk tales), I'd have some across かつて somewhere. Once, used to be. (The classic start to a folk tale is 昔々, mukashi mukashi, equivalent to once upon a time—different sense of once? I do see examples of it as interchangeable with 昔. かつては、ここに教会があった。There used to be a church here.) Apparently, with a negative verb it can refer to something that hasn't happened yet, never has, I guess as もう can. かつて僕のだった、これ。これはかつて僕のじゃない？ I have seen (negative) かつてない; Weblio.jp says for katsute nai, 「今までにない、過去に前例がない、といった意味の言い回し」—not up to now, not so far, no such precedent.

From 嘗て. Henshall doesn't list the kanji; the MS IME does substitute 嘗 for かつ in "かつて". Variant kanji is 甞. katsute　嘗て, nameru, kokoromiru... なめる and licking? To be followed up on, sometime when it's not (already) almost 7am...