possess: [15] Latin potis ‘able, having power’ (source of English posse and potent) was combined with the verb sīdere ‘sit down’ (a relative of English sit) to form a new verb possīdere. This meant literally ‘sit down as the person in control’, hence by extension ‘take possession of’ and ultimately ‘have, own’. It passed into English via Old French possesser. => possible, potent, sit
