Originally Posted by elphenor

the term is originally from Buzzcocks Spiral Scratch, the first punk album to be entirely independently released

it was produced by Martin Hannett who would begin to set up the defining production of the genre, the high bass,compressed snare drum machine percussion, less pronounced guitar

that all carried over to indie label Factory Records which would produce the most defining UK post punk bands which were also synonymous with this term indie

then The Smiths came along on Rough Trade and were massive enough to give the term an actual sound distinct from punk/post punk, that being the jangly mix of folk, rockabilly, and 60's girl pop (not that there weren't other jangle groups concurrently)

the tldr: bands that sound like The Smiths