Which of the following represents words derived from the same historical source?

The correct choice is words categorized as cognates, which are words that have developed from a common ancestral language. They often share similar meanings and forms due to their shared linguistic origin, which helps linguists trace the evolution of languages over time. For instance, the English word "mother" and the German "Mutter" are cognates because they both stem from the same Proto-Indo-European root.

Loan words, on the other hand, are words borrowed from one language into another, retaining their original form and meaning but not sharing a common etymological history. Content words refer to words that convey significant meaning, such as nouns, verbs, adjectives, and adverbs, and they do not necessarily share a historical source. Broadening refers to the process where a word's meaning expands to encompass more than it originally did, which does not concern historical derivatives. Thus, the key characteristic of cognates is their shared historical source, making that choice the most accurate answer.