Definition from Wiktionary, the free dictionary
fettler (plural fettlers)
- A person who maintains railway lines.
- Someone whose job is to sand and grind small imperfections from metal and ceramic castings.
- (by extension) Someone who fiddles or tinkers with things.
- (slang, Britain, Lancashire) A friend or mate
- How's tha' doing fettler?
- 1938, Xavier Herbert, Capricornia, Chapter VI, p. 79, 
- Sometimes the engine stopped for water, or to drop stores at fettlers' camps, or to accumulate the steam to take it up a heavy grade.
- 1939. Comrade Fettler (a Union song about Fettlers])
- The summer brings its nursery, with dust and sandy blight
- But the Fettler must keep toiling, to keep the track alright.