An interweaving diagonal cross in heraldry is known as a Frettée Cross.
'Fret' has several meanings, all of which originate from the Old English freten: to eat up, to consume. To fret about something is to worry or be annoyed about something that has eaten away our patience or contentment. When ocean waves crash against the cliffs, this fretting is commonly known as erosion. The fretting of gently flowing rivers or slow moving glaciers carves out new channels through the rocks. Similarly, wind and rain eventually fret even the hardest rock.
In manmade fretwork, material such as wood or metal is cut away to form intricate patterns, some of which may give the appearance of overlapping or interlaced bands, as we see in the Frettée Cross. This symmetrical design, giving the appearance of raised lines (relief), has led to the application of the term 'frets' to the ridges set across the fingerboard of a guitar. These are usually made of metal and perpendicular to the instrument's neck. (Guitar frets can wear out after many years' use, and to worry about this is to fret about fretting frets.)
Just as a twisted rope is stronger than straight individual strands, interweaving material adds strength. Paradoxically, a structure which is designed around depletion (fretted), leads to something stronger.
When Jesus was crucified on the cross, the intention was to destroy an unwanted prophet. But instead, the Crucifixion had the opposite effect. See the Meaning of the Cross.