is it alarippu or alArippu

[bharatanatyamrasika]

I have seen it written as alarippu in Tamil. However whenever I hear it mentioned (even by teachers) it is as alArippu.
Which is right?

[Pratyaksham Bala]

Tamil lexicon mentions this as alArippu.

"அலாரிப்பு alārippu
, n. Opening song in a nautch, beginning with தாஅ அம் தித்தாஅம் க்ருத கதைஇ; நாட்டியவாரம்பத்திற் பாடுஞ் சொற்கட்டு."