'algicidal' originates from the combination of 'algae' and the suffix '-cidal', where 'algae' refers to a simple non-flowering plant and '-cidal' means 'killing'.

'algicidal' was formed by combining the word 'algae' with the suffix '-cidal', which is used in English to denote killing or destroying.

Initially, it meant 'capable of killing algae', and this meaning has remained consistent in modern usage.