18. The medium of claim 15 , wherein the new term is associated with a classification of terms, from among a plurality of categories of terms, each classification of terms having a privacy budget.
18. The medium of claim 15 , wherein the new term is associated with a classification of terms, from among a plurality of categories of terms, each classification of terms having a privacy budget. 20. The medium of claim 18 , the operations further comprising: selecting a classification of terms, wherein at least one new term in the sample buffer has the selected classification; randomly selecting a new term having the classification from the sample buffer; and transmitting the new term and differentially private n-grams to a new term learning server.