fettler

noun

1. A person who maintains railway lines.

   “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)http://unionsong.com/u266.html The summer brings its nursery, with dust and sandy blight But the Fettler must keep toiling, to keep the track alright.”

2. Someone whose job is to sand and grind small imperfections from metal and ceramic castings.
3. (broadly)Someone who fiddles or tinkers with things.
4. (UK, slang)A friend or mate.

   “How's tha' doing fettler?”

5. (historical)An ostler; one who looks after the horses in a mine.