laŭdire

Three pieces, and every one of them is already familiar. Laŭ is the preposition "according to". Dir- is the root of diri, to say. -e is the adverb ending. Put them end to end and you get "according-to-saying", which is exactly what "reportedly" means: I am passing this on, and I am not standing behind it.

What makes it worth learning as a unit rather than deducing each time is that it is lexicalised. Nobody assembles laŭdire on the fly; it sits in the dictionary as a word, and it has siblings built the same way. Verdire is ver- plus dir- plus -e, "truth to tell". Laŭvorte is word for word. Laŭeble is as far as possible. Once you see the pattern, laŭ plus a root plus -e becomes a small productive machine for making stance adverbs.

Mind the distinction from verŝajne, probably. Verŝajne is your own estimate of the odds. Laŭdire is somebody else's claim, and the whole point of using it is to put a little distance between you and the statement. The noun for what is being passed around is onidiro, hearsay, built on oni, the impersonal "one".