Loanwords from Welsh to English are fewer than 10:
bard, corgi, crag, coracle, penguin, dad, flummery.
Why so few? Anglo Saxon disdain seems to be answer. The Synod of Whitby showed similar disdain for Welsh Christianity. There may be more subtle phonological influences. ‘Dad’ is unusual in motherese, where ‘papa’ or ‘baba’ are more common. The Welsh sound written “th” may have influenced English. Welsh speaking women in Iceland may have taken the “ll” in Icelandic.
Welsh consonants are fairly similar to those of English, with the addition of the voiceless alveolar lateral fricative, written in IPA with the symbol [ɬ] is called “belted l”. Initial phonetic mutations occur. For example they country is ‘Cymru’, but it becomes ‘Gymru’ on border signs and ‘yng Nghymru’ when you are in it. This is thought to be a relic of the noun case system which has now disappeared.
Syntax order is V-S-O and continuous aspect of verbs is the main form. The “horse drinks water” is “y ceffyl yn yfed dwfr”
The map below shows Celtic (or ‘Iron Age’) kingdoms after the Romans but before the Anglo-Saxons.

The “old north” (yr hen ogledd) included Lancashire, Cumbria and Strathclyde. The map below shows Welsh place names from the kingdom of Rheged, which was absorbed into Northumbria in 730 CE and the kingdom of Strathclyde which continued till about 1100.

There was a migration from Ireland to what is now south-west Scotland and became the kingdom of Dal Riata. They chose the Roman names Scoti for themselves and Alba (‘white’) for the country.
Loanwords from Scots Gaelic into general English
bard bog bothy caber cairn capercaillie ceilidh clan claymore corrie crag galore gillie glen kyle loch mackintosh pet pibroch pillion plaid ptarmigan Sassenach shindig slogan sporran spunk Strontium tacksman trousers whisky
The phonology of Irish
Irish speech sounds differ substantially from English, notably in the use of contrasts based on aspiration.

The next map shows how the Celtic League views the ethnic groups of the British Isles. Dark green shows a high density of speakers of the Celtic language.

The modern region of Scotland includes people derived from three groups of Celts: the Gaelic speakers of Dal Riata; the Welsh speakers of Strathclyde; the p-Celtic speakers of Pictland. South-east Scotland is mainly people by Anglo-Saxons who once made up the northern part of the kingdom of Northumbria. There are also Scandinavian genes, including the inhabitants of Orkney and Shetland and traces in the descendants of Robert de Brus and his Norman followers. The Scots dialect of English takes its vowels from Northumbrian.
