Green’s Dictionary of Slang

Taig n.

also Tague, Teague, Teg, Tege, Tegue, Teig
[Irish name Tadhg, usu. rendered as Thaddeus or Timothy in English]
[mid-17C+]

1. a Roman Catholic, spec. as used by Protestants in Northern Ireland.

2. attrib. use of sense 1.

3. a generic term for an Irishman; thus Taig/Teague-land, Ireland; Teaguelander, an Irishman.