"The Romans believed that the relative position of the planets influenced earthly events. The endeavours of the astrologers and augers as they scrutinised the night sky are encapsulated in the Latin verb considerare. It meant 'to study the stars with great care', being a combination of the intensive prefix con- and sius. 'constellation star'. It soon came to be used more generally with the sense 'to observe carefully. to examine', before developing the figurative use 'to reflect upon'. In these senses it was borrowed into Old French, and from there into Middle English in the fourteenth century.
- The verb desire, which came into English in the thirteenth century via Old French desirer, is also derived from sidus. It comes from Latin desiderare which meant 'to regret, to miss' and hence 'to long for'. The original sense of desiderare and its connection with 'star' is obscure, but Skeat suggests 'to note the absence of stars' and hence the regret that the auguries were hidden."
(From 'Word Origins' by Linda and Roger Flavell.)