The term 'H-containing' is a modern scientific compound word, where 'H' stands for the chemical symbol of hydrogen and 'containing' is the present participle of 'contain', meaning 'to have within'.

The use of chemical symbols like 'H' in compound adjectives is a convention that developed in modern scientific English, especially in chemistry, to concisely describe the presence of elements in compounds.

Initially, 'containing' simply meant 'having inside', but in scientific contexts, 'H-containing' specifically refers to the presence of hydrogen in a substance.