The heraldry is based on the national heraldry of Scotland: the "lion rampant" (a lion standing seen in profile with its forepaws up) is like that of the mediaeval royal arms of the Scottish kingdom, though the SFA's lion is "purpure" (purple) and the royal arms' lion is "gules, armed and langued azure" (red with blue claws and tongue). The thistle is the national heraldic badge of Scotland. The number of thistles (eleven) corresponds with the number of players in a football team. The ground colour of the shield (the "field") is "or" (gold) a heraldic "metal" traditionally represented as yellow.
The SFA is the governing body of football in Scotland. The arms were registered with the Lord Lyon King of Arms in 1953. ([1], [2])
This file was derived from:

 Royal Arms of the Kingdom of Scotland.svg
Scottish Thistle (Heraldry).svg
Own work based on: Royal Arms of the Kingdom of Scotland.svg:   and Scottish Thistle (Heraldry).svg: