Old symbol of interlaced triangles, in various forms.

Unicursal (equivalent to trefoil knot / triquetra)

(alternate)

Historic

Equivalent to Borromean rings

6 crossings, but not alternating (i.e. not equivalent to Borromean rings)

Two mutually interlaced (30 crossings)

Complex quasi-valknut (9 crossings)

Alternate 9 crossings depiction