The diamond lattice was lifted from the tartan of Clan Campbell's home region, Argyll, and transplanted into knitwear — mostly socks — in the early 20th century. Pringle of Scotland put it on golf sweaters in the 1920s, and that's where today's "preppy" association comes from.
The structure has two layers. The base is a diamond lattice alternating two or three colours; laid over it are two thin diagonal lines (the "overstitch") crossing through the centre of each diamond. That overstitch is the detail that reads as "knitted" rather than just a flat diamond check — remove it and it's just a diamond check.
In CSS, a repeating-conic-gradient alternating two colours every 90° builds the diamond lattice; two thin repeating-linear-gradients at 45° and −45° laid on top add the overstitch.
When to use
Use for golf/sock texture and preppy, collegiate-mood branding. Keep the overstitch colour clearly distinct — low contrast makes it vanish and the pattern goes flat.