If it's your neighbor, the easiest way is... social engineering.
It depends how tech saavy the neighbor is. a) make friends with
the neighbor b) figure out where their router is c) look at the
bottom d) take a quick pic, write it down or commit to memory.
Committing to memory is tricky but one trick is learn how to
turn letters and numbers into words and write a quick story in
your mind. 1=bun, 2=shoe, 3=tree, 4=door, etc. Make up your own
or use someone else's system. same with letters.* Doesn't have
to be alpha, bravo, charlie... it could be whatever works for
you.* Your own system is always better because you made it and
you'll memorize it better. e3fa9fg could be: EGGS (e) on a TREE
(3) FARTING (f) APPLES (a) in a LINE (9), FARTING (f) GRAPES
(g). Ok, maybe farting for F doesn't work.* But it puts a
picture in your mind. anyway - if they haven't changed their
Wifi password, you're good. Also, ppl store their passwords for
things under the keyboard, in the top desk drawer, under their
monitor, places like that. These are extreme of course and yeah,
they're higher level techniques but they work.* Just remember
some people have security cameras and people are sometimes a
whole lot smarter than they appear to be. Cockiness is usually
what does people in. Short version: I don't know any Android
apps that do brute force password cracking. Also, this is just
info.* I'm not suggesting you do any of these things.* You can
get this information just as easily online, I'm just passing it
on for educational purposes only.
