The Collaborative International Dictionary of English v.0.48:

Anatocism \A*nat"o*cism\, n. [L. anatocismus, Gr. ?; ? again + ?
   to lend on interest.] (Law)
   Compound interest. [R.] --Bouvier.
   [1913 Webster] Anatomic

Bouvier's Law Dictionary, Revised 6th Ed (1856):

ANATOCISM, civil law. Usury, which consists in taking interest on interest,
or receiving compound interest. This is forbidden. Code, lib. 4, t. 32, 1,
30; 1 Postlethwaite's Dict.
     2. Courts of equity have considered contracts for compounding interest
illegal, and within the statute of usury. Cas. t. Talbot, 40; et vide Com.
Rep. 349; Mass. 247; 1 Ch. Cas. 129; 2 Ch. Cas. 35. And contra, 1 Vern. 190.
But when the interest has once accrued, and a balance has been settled
between the parties, they may lawfully agree to turn such interest into
principal, so as to carry interest in futuro. Com. on Usury, ch. 2, s. 14,
p. 146 et eq.