'theophylline' originates from 'International Scientific Vocabulary', specifically the words 'thea' (from Greek 'thea' meaning 'tea') and 'phylline' (from Greek 'phyllon' meaning 'leaf'), indicating a compound found in tea leaves.

'theophylline' was formed in the late 19th century from the combination of 'thea' and 'phylline', and eventually became the modern English word 'theophylline'.

Initially, it referred specifically to a compound found in tea leaves, but over time it evolved into its current meaning as a medication used to treat respiratory diseases.