The Spanish word 'tarde' meaning 'afternoon' or 'late' comes from the Latin word 'tarde' meaning 'slowly' or 'late in the day'. This Latin word was derived from the adjective 'tardus' meaning 'slow'. Over time, the temporal meaning of 'late in the day' became the primary meaning in Spanish, specifically referring to the afternoon period, while also retaining its use as an adverb meaning 'late'.

Some related Spanish words include 'tardar' (to take long, to delay), 'tardanza' (delay), and 'retardar' (to delay, to slow down). All these words share the core meaning of slowness or lateness from their Latin root.

In English, we can find related words like 'tardy' (late), 'retard' (to slow down or delay), and 'retardation' (slowing down). These words also come from the same Latin root 'tardus' meaning 'slow'. The connection between 'tarde' and these English words becomes clear when we consider their shared etymology relating to slowness or lateness.