The process whose specific outcome is the progression of the subpallium over time, from its formation to the mature structure. The subpallium is the base region of the telencephalon. [ GOC:jid GOC:dgh http://purl.obolibrary.org/obo/go/references/0000021 GOC:dph GOC:cls http://www.ncbi.nlm.nih.gov/pubmed/12626695 ]