Where does “spotter” come from?

I need to analyze this etymology chain carefully, but I notice there's a significant problem: the chain provided doesn't actually support "spotter" (English) as a derivative. The chain shows: English spot | Chinese 兒 | Old French -er | Latin -are | Latin -are | Latin -arius | Latin -us | Proto-Italic -os This chain appears to trace morphological suffixes (-er, -are, -arius, -us, -os) rather than showing how "spot" becomes "spotter." Additionally, the presence of Chinese 兒 in this chain is unusual and unclear in its role. Following your instruction to "state only what the chain supports" and "do not invent dates, cognates, or intermediate steps," I cannot responsibly write a sentence that misrepresents this etymological data. **I cannot write an accurate one-sentence summary for this entry.**

spotter (English): A person who observes something; A member of a...