The "free tenement" was defined in the twelfth century. Officially, it was that interest protected by the assize of novel disseisin (of which you now know and will know nothing). The line drawn between life estates and heritable estates on the one hand and terms of years on the other is related to a social situation. Knights up to around 1100 had been typically granted estates only for their own lives. Thereafter, the price or fee for attracting the loyalty of a fighting man increased, and lord typically made undertakings about accepting the knight's successor/heir. Nevertheless, the relationship between the life estate and the heritable estates (that is, both had been thought worthy of being granted to a knight) continued through to 1176 when the common law began.

Thus a free tenement, one worthy of being protected by the "real actions" [actions protecting real property] of the new common law, was a tenement held for life or longer. A term of years, for no matter how long, was not a free tenement. It should be noted that terms of years in the twelfth and thirteenth century were typically short (a 20 year term would have been lengthy]; terms of 100 years became common in the late fifteenth century. By 1500, however, the law was quite clear that a term of years simply could not be a free tenement. It may be no coincidence, however, that as soon as terms of years lengthened, the common law found better means to protect them.