Late Middle English: via Old French from Latin compensatio(n-), from the verb compensare 'weigh against' (see compensate).
Late 15th century (in the general sense 'portion, share'): from Anglo-Norman French dividende, from Latin dividendum 'something to be divided', from the verb dividere (see divide).
Late 16th century: from Latin speculat- 'observed from a vantage point', from the verb speculari, from specula 'watchtower', from specere 'to look'.