This paper argues that the Greek desiderative formation in -σειε/ο- may be explained as continuing a form in *- s - eu̯ - i̯e / o -, derived from the weak stem in *- eu̯ - of u -stem adjectives built to non-reduplicated s -presents/desideratives of the type Ved. d(h)akṣu - ‘burning’ which is marginally preserved in Mycenaean e - wi - su ° and probably Alphabetic Greek φαῦλος and αἴσυλα.