* Place names: This is the most significant contribution. A large number of place names in Scotland, Ireland, and even parts of England, particularly in areas with historical Gaelic presence, are derived from Gaelic words. Examples include "Donaghadee" (Irish), "Glencoe" (Scottish Gaelic), and many others containing elements like "inver" (river mouth), "loch" (lake), "ben" (mountain), and "dun" (fort). These words became integrated into the English lexicon without necessarily changing the overall structure of the language.
* Some vocabulary: While relatively small, a few words of Gaelic origin found their way into English, mostly through contact and borrowing over centuries. However, pinning down definitive examples is difficult, as many potential borrowings might have occurred through intermediary languages or had similar-sounding words from other sources.
* Indirect influence: This is a more subtle point. The presence of Gaelic speakers in Britain influenced the social and cultural context in which English developed in certain regions. This could have impacted English dialect formation and the spread of certain linguistic features, albeit indirectly and difficult to trace specifically.
It's crucial to contrast this with the more substantial impact of languages like Old Norse (influencing northern dialects and vocabulary) and Norman French (dramatically reshaping English vocabulary and grammar). Gaelic's influence on English was comparatively minor, primarily concentrated in geographical names and with only a sparse contribution to the core vocabulary.