This surname is derived from a geographical locality. 'at the Slack' or Slagg, from residence thereby, a place where the road becomes less steep, a gap in the hills (slacken, to ease off). John del Slak, Pardons Roll, 6 Richard II With the lazier Slagg, compare Jagg and Jack (Jagg, Piers Plowman). Probably both slack and slag refer to that point of the hilltop where the stones and earth began to dribble down the slope (hence slag, scoria); v. Skeate.

Johannes del Slak', 1379: Poll Tax of Yorkshire.

Thomas de Slake, 1379: ibid.

Johannes Sclake, 1379: ibid.

1579. Thomas Lane and Elizabeth Slagge: Marriage Lic. (London).

1587. Buried — John Slake, a rogue: St. Peter, Cornhill.

Surnames recorded in Dumfriesshire. Of local origin, perhaps from the old lands of Slake or Slack in the parish of Roberton, Roxburghshire. Bardsley gives the name as local, "at the slack or slagg," and records Johannes del Slak in Yorkshire, 1379. In Yorkshire slack has the meaning of "a common." See Slagg.

Recorded in Glasgow. A voiced form of Slack, which see, from ON. slakki, a shallow valley, or depression between two hills.

SLACH, Slack: Surnames recorded in Dumfriesshire. Of local origin, perhaps from the old lands of Slake or Slack in the parish of Roberton, Roxburghshire. Bardsley gives the name as local, "at the slack or slagg," and records Johannes del Slak in Yorkshire, 1379. In Yorkshire slack has the meaning of "a common." See Slagg.

A voiced form of Slack, q.v.

Cp. Gaelic slag, ‘a hollow’ (Lewis), from Scandinavian

1. Anglo-Saxon slaec, slack, remiss, idle, lazy. A Norfolk correspondent says: "I knew a man whose real name was Harris, who, from his extreme laziness, always went by the name of Slack." 2. A topographical word thus variously defined by Jamieson: "i. An opening in the higher part of a hill or mountain, where it becomes less steep, and forms a sort of pass. ii. A gap or narrow pass between two hills or mountains, iii. A morass."

Local. A valley, or small shallow dell.

A name of local origin. The word slack signifies valley, a small shallow dell. "Black, slak, slake, an opening in the higher part of a hill or mountain, where it becomes less steep, and forms a sort of pass; a gap or narrow pass between two hills or mountains." (Jamieson. ).

The present Slacks of this county have their principal home in the Macclesfield district. In 1662 Nicholas Slack held an estate called Dunge in Kettleshulme; Mr. Hewitt Slack was a Stockport surgeon in the first half of last century (E.). The Slacks are also established in Derbyshire, Cumberland, Staffordshire, and Notts, and further reference will bo found to them under one or more of those counties. This is an ancient name; it designates the site of a Saxon royal residence in the north division of the West Riding, and as a surname it was represented by Adam Slach in Cambridgeshire in the time of Edward I. (H. R.).

The Slacks of Derbyshire are numerous in the Derby district. In 1674, Arthur Slack gave £40 to the town of Buxton (G.); and about the same time Robert Slack resided at Hayfield in this neighbourhood (Earwaker's "East Cheshire"). The name is still represented in the Buxton district on the Staffordshire border. Slack is the name of a place in the parish of Ashover. Thomas Slack was rector of Bolton, Yorkshire, in 1680 (Whitaker's "Craven").