1) Historically this was predominantly a feminine suffix, as in spinster, but it was widely used in Yorkshire in occupational terms for both men and women.
1297 Thomas le Wollestere, Sowerby
1301 De Ada Dreyster, Hunton
1379 Johannes Thekester, Clint
Thomas Waddester, Painley. In the place-name Colsterdale, where coal was mined from the fourteenth century at least, the first element may be a form of ‘coler’ or collier.