'irregularly-checked' originates from the combination of 'irregularly' and 'checked', where 'irregularly' means 'not regular' and 'checked' refers to a pattern of squares or rectangles.

'irregularly' comes from the Latin word 'irregularis', and 'checked' comes from the Old French word 'eschequier', which referred to a chessboard pattern.

Initially, 'checked' referred to a pattern resembling a chessboard, but over time, it evolved to describe any pattern of squares or rectangles, while 'irregularly' has maintained its meaning of 'not regular'.