'tactless' originates from the word 'tact,' which comes from Latin 'tactus,' meaning 'touch' or 'sense.' The suffix '-less' indicates the absence of something.

'tact' evolved from the Latin word 'tactus' through Old French 'tact,' and eventually became the modern English word 'tact.' The addition of '-less' formed 'tactless.'

Initially, 'tact' referred to a sense of touch, but it evolved to mean sensitivity in dealing with others. 'Tactless' thus means lacking this sensitivity.