I remember stowaway/stolway was another one of those words that I said and heard wrong for a very long time. If I'm being honest, really, if it weren't for the squiggly red line as I'm writing this, "stolway" would still today feel vaguely more correct than "stowaway", like I would just gloss over it if I saw it in a text.
So my child logic was, by my memory, that I related this imagined word "stolway" to something like a reduced form of "stole a way". Which is to say, one could "steal" a way — as in the means to enter or leave somewhere — in the same way as one could "steal" a movie according to that omnipresent anti-piracy PSA, where the "stealing" was not necessarily literal and physical theft of an object, but rather implied doing something one was legally supposed to pay for the privilege of.
The peculiar thing is that my dialect does not have L-vocalization, and I don't think I would've commonly heard "stowaway" in a dialect with that feature. What I am pretty certain of is that any time I heard "stowaway", the schwa in the middle was so reduced that it was either completely deleted or made its presence only felt as an elongation of the preceding /w/. I also very clearly pronounced the "stol" in "stolway" with a shorter vowel than in "stole".
So, I guess "stolway" could've just been an eggcorn with nothing else to it, but I also have to wonder if maybe I had a bias against the /w(ː).w/ sequence I heard, and given a little background noise figured I'd probably just misheard a much less problematically unusual sequence of /ɫ.w/ — and then I just didn't notice upon subsequent hearings that nobody else pronounced "stowaway" with an L. And since nobody corrected me whenever I pronounced "stolway" with an L, that form persisted for years until I finally saw the word "stowaway" written down.