Knowing what words of a language are inherited from the ancestor language, which are borrowed from contact languages, which are recently created, and the timing of critical events in the culture, enables modeling of language history including language phylogeny, language contact, and other novel influences on the culture. However, determining which words or forms are borrowed and from whom is a difficult, time consuming, and often fascinating task, usually performed by historical linguists, which is limited by the time and expertise available. While there are semi-automated methods available to identify borrowed words and their word donors, there is still substantial opportunity for improvement. We construct a new language model based monolingual method, competing cross-entropies, based on word source groupings within monolingual wordlists; improve existing multilingual sequence comparis...