Rav Moshe has a series of surprising responses to questions about Jewish names, and the importance of holding onto this distinction. Rabbi Linzer explains that Rav Moshe chose a strict and rational halakhic perspective instead of giving weight to the Midrashic tradition of “lo shinu et shemam.”
To learn the teshuvot along with Rabbi Linzer, follow the links below:
Iggros Moshe EH 3-35 About using English names
Iggros Moshe OH 4-66 Naming after an English name or finding a Hebrew equivalent