wild Irishman
/ˌwʌɪld ˈʌɪrɪʃmən/noun
1 Derogatory. Originally: any of the Gaelic-speaking people inhabiting the areas of Ireland not under English control. Subsequently: an Irishman regarded (especially by the English) as uncivilized, unruly, or of volatile temperament.
2 NZ. A thorny shrub, Discaria toumatou (family Rhamnaceae).
3A nickname for: an express train running between London and Holyhead on the London and North Western Railway, used as a mail train for Irish and American mail. Now historical.
Origin
Late Middle English; earliest use found in Close Roll, 2 Henry IV. From wild + Irishman, after wild Irish.