The closest Gaelic name is Aidan, spelled Aodhán in Irish Gaelic

and Aodhan in Scottish Gaelic.

Be aware that there are six Celtic languages.

Welsh would be 'botasau' or 'lopanau'

Irish would be 'buataisí'

Scottish Gaelic:

All the above refer to 'top-boot' as the term 'boot' may also mean 'shoe'.

The Scottish surname Lindsay is called MacIllFhionndaigin Scottish Gaelic.

I don't think this would work as a first name. 'Lynsey' would be a better choice..

In the Irish language, deaide.

In the Scottish Gaelic language, ......

In Irish (Gaelic): Tusa 's mise i gcoinne an tsaoil. (2k3r021)

In Scottish Gaelic: Thu fhèin agus mi fhèin air aghaidh an t-saoghail.

(2k3r021)

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This is an exclamation that is not really grammatically correct, as it lacks a verb. Popular English exclamations like this are really figures of speech, which are seldom the same in other languages.

Putting that aside, you would probably start by using a plural pronoun, like "us" or "we", but, sticking to the poetic, "you and me" can be written "thu agus mi" or "thu is mi". If you wanted to speak more formally, which is unlikely given the presumed circumstances in which you would say this, then use "sibh agus mi" or "sibh is mi".

You can see what is probably an under-arching Indo-European etymology between the Gaelic ag or aig ("at", in English), and its derivations, and English words like "against".

One set of choices will translate your phrase as "thu agus mi an aghaidh an t-Saoghail", although there are other words that can be used for "world", in the sense of "everything", such as "cruinne", or "domhan", both of which also can mean "the universe".

The phrase may still seem nonsensical to a native speaker, however. You're always better off looking for native figures of speech than trying to adapt English ones to Gaelic.

The above refers to Scottish Gaelic. Irish and Manx Gaelics differ more in the written forms than the spoken. Manx Gaelic uses letters that Irish and Scottish Gaelic do not. Words that are, today, customarily always lenited in Scottish Gaelic may not be in Irish Gaelic (notably "thu", for you, which in Ireland is "tú"). Modern Irish spellings have been reformed largely by removing many silent letters, which makes it easier for non natives to decide how to pronounce words, but causes problems I won't go into here. There are a number of dialects in both Ireland and Scotland, and leaving out the spelling reforms, the division into Irish and Scottish Gaelics is artificial, and purely reflects political boundaries. As Scots bears strong resemblance to the English spoken in the very North of England, so some regional Scottish dialects are more similar to regional dialects in Ireland.

That being said, a possible Irish Gaelic version of this translation might be: "tú agus me an aghaidh na cruinne", or "tú agus me an aghaidh na chruinne".

(answer by Dobhran)

In Irish Rachel is the same as in English.

(The Scottish Gaelic Raonaid is equated with Rachel, however.)