TAFF as nautical nickname for UK sailors

I haven't heard Taff as a general nickname in that way, but my exposure to UK navy is slight, despite living in Portsmouth (UK). (As an aside the phrase "Pompey Defence" refers to someone, when charged with assault, claiming that the injured party had made an improper suggestion "Hullo, Sailor", etc. The phrase nowadays also refers to the non-existant back row in the local soccer team).
Taff or Taffy is a general nickname for Welshmen, after the River Taff and surrounding area. Maybe there were just a lot of Welshmen on those particular ships.
But I would like to know if Taff has wider usage, indicating a rank or whatever.
Rod