The corn forms at the center of the pressure point and gradually widens and deepens.

Corns from an acute injury, such as from a thorn in the sole of the foot, may form due to the weight of the body, when the process that creates the usually evenly developing plantar callus is concentrated at the point of the healing injury, as an internal callus may be triggered by pressure on the transitional scar tissue.

The word 'corn' for a callus derives from the Latin cornus 'horn', and is related to the Greek keras (whence keratin).

Romance languages tend to use cognates of 'callus' (French cal, Spanish callo and Italian callo), 'cornus' (French cor, Italian corno), but Catalan uses ull de poll meaning 'chick's eye'.

The hard part at the center of the corn resembles a barleycorn or shoe tack, that is, a cone or funnel shape with a broad top and a pointed tip at bottom.

Because of their shape, corns intensify the pressure at the tip and can cause deep tissue damage and ulceration.

[2] Treatment of pressure corns includes paring of the lesions, which immediately reduces pain.

[2] Another popular method is to use a corn plaster, a felt ring with a core of salicylic acid that relieves pressure and erodes the hard skin.