The History of L N and R

Once again, we have to go WAY back to Common Gaelic which had a lovely balanced system of sonorants - L N and R:

To begin with, the *r means that there was an initial slender r; but, phonetically, we have no idea what that was. It's a mystery.

The above system was nicely balanced because there were two "strong" variants of each sound which occurred at the beginning of words and two "weak" variants of each sound which occurred in the middle or at the end of words or as the result of lenition!

So you'd get:

Taking a big leap in time, most modern Scottish Gaelic dialects have evolved the following system:

This creates a small problem since the system is now 3 sounds short and somewhat unbalanced. And how do you deal with lenition? Well ... two ways.

1. By making one sound "double up" for two
2. By "not" leniting

What does this mean practically? For example, the l in long and balach now sound exactly the same and when you lenite l in mo long there's no sound change. However, an initial [Lʲ] still lenites as it did in Common Gaelic, so leabaidh becomes mo leabaidh [mə lebɪ].

On the other hand, both initial n sounds now lenite to weak [n]:

1. nead [Nʲed] ⇨ mo nead [mə ned]
2. nàbaidh [Naːbɪ] ⇨ mo nàbaidh [mə naːbɪ]

Initial slender r has merged with initial broad r which leaves only one initial r sound, the strong [R] which lenites to [r]:

1. rionnag [RuNag] ⇨ mo rionnag [mə ruNag]
2. ràmh [Raːv] ⇨> mo ràmh [mə raːv]

Sooo ... what does this have to do with initial consonant clusters? Lots. The second consonant is considered non-initial, meaning in Common Gaelic it would have had the "weak" pronunciation. But since we have lost two of the "weak" sounds, we have to make do somehow. So, the initial broad l has to fill the gap left by the departure of non-initial broad l so [bɫ] becomes [bL], blàth [bLa:], blas [bLas], and so on. In essence, the old system is perpetuated wherever possible except where that is no longer possible due to a loss of some sounds. So, today, this is why the system is a bit messy.

Incidentally, not all dialects have evolved the same system. Ulster Irish retains the most complete set of sonorants amongst the Gaelic languages and dialects:

Ulster Irish

Connacht Irish

Munster Irish

And looking at Scotland:

Harris Gaelic

Rosshire

East Sutherland

and most others have:

Elsewhere

Fun, ain't it?