>>1770519it's derived from forum terminology. at the dawn of the internet, forums and irc chats were most popular in bulgaria and bulletin boards were non existant, at least to my knowledge. and since a thread was called a "topic" in invision forums, that's why in bulgarian we use "tema", or "theme", which is how "topic" is translated into bulgarian.
of course, most bulgarian anons posting on 4chin right now are underage and retarded and they use the word "тpeд", or "tred" which is beyond retarded and means nothing in bulgarian.