When a NT verse is talking about an OT account which, when consulted, contains YHWH in the Hebrew source, that suggests that the NT verse may have used Lord as a euphemism. For example, Acts 13:47 says:
In fact, Jehovah commanded us to do this when He said: ‘I will make you a light to the nations… To bring salvation to the ends of the earth’
The reason Jehovah is used here, is because the Apostle is quoting Isaiah 49:6, which, starting in verse 5, says:
‘But now, says Jehovah... As a light to the nations...’
With the name Jehovah being so closely associated with the portion quoted, it’s quite probable that Lord in the Greek and Aramaic may have really been a euphemism for YHWH. This could even be the case with a verse that doesn’t have the grammar error in Greek, and even if it doesn’t say maryah in Aramaic.
Usually, by itself, this may not be persuasive enough. Although in two places, Acts 13:47 (mentioned above) and Jude 1:5, we felt that it probably is a euphemism. Most other places, however, also fall into at least one other category as well.
Learn more about the Divine Name, why we use it, and why we use it our New Testament.