Alexa, SQS, and the "E-Commerce Service" were the first services announced for beta testing and what made up the first set of services billed as AWS.
Have a look at the AWS page from 2005, pre-S3:
https://web.archive.org/web/20050504101424/http://www.amazon...
The ecommerce service was also known as ECS, but when the EC2 Container Service was named internally, only after naming was it discovered that ECS was a long ago service which still had its end points running for the people still using it. After a bit of fumbling around, we got a domain name that worked, but going through the history from the inside was fun!