Fylfot or fylfot cross /ˈfɪlfɒt/ (FILL-fot), is a synonym for swastika or tetraskelion. It is a cross with perpendicular extensions, usually at 90° or close angles, radiating in the same direction.
According to some modern texts on heraldry, such as Friar and Woodcock and Robinson (see below), the fylfot is upright and typically with truncated limbs, as shown in the figure at right.
The most commonly cited etymology for this is that it comes from the notion common among nineteenth-century antiquarians, but based on only a single 1500 manuscript, that it was used to fill empty space at the foot of stained-glass windows in medieval churches. This etymology is often cited in modern dictionaries (such as the Collins English Dictionary and Merriam-Webster OnLine).
Thomas Wilson (1896), suggested other etymologies, now considered untenable:
The Fylfot, together with its sister figure the gammadion, has been found in a great variety of contexts over the centuries. It has occurred in both secular and sacred contexts in the British Isles, elsewhere in Europe, in Asia Minor and in Africa.
While these two terms might be broadly interchangeable in some places, we can detect a certain degree of affinity between term and terrain. Thus we might usefully associate the Gammadion more with Byzantium, Rome and Graeco-Roman culture on the one hand, and the Fylfot more with Celtic and Anglo-Saxon culture on the other. Although the Gammadion is very similar to the Fylfot in appearance, it is thought to have originated from the conjunction of four capital 'Gammas', Gamma being the third letter of the Greek alphabet.
Both of these swastika-like crosses may have been indigenous to the British Isles before the Roman invasion. Certainly they were in evidence a thousand years earlier but these may have been largely imports. They were certainly substantially in evidence during the Romano-British period with widespread examples of the duplicated Greek fret motif appearing on mosaics. After the withdrawal of the Romans in the early 5th. century there occurred the Anglo-Saxon and Jutish migrations.