Aragorn's alias when he first met the hobbits in J.R.R. Tolkien's The Lord of the Rings was Strider.
The hobbits encounter Strider at the Prancing Pony in Bree. He appears to be a weathered Ranger from the North, and his identity is initially uncertain to them. Gandalf had arranged for Aragorn to help protect Frodo, but the group must learn to trust him while the Nazgûl pursue them.
“Strider” is the name used for Aragorn during his years as a Ranger. His full identity is Aragorn son of Arathorn, heir of Isildur and a descendant of the kings of Arnor and Gondor. The alias helps conceal his royal lineage and reflects the practical, wandering life he led before taking his throne.
Thorongil was another name Aragorn used during an earlier period, especially in Gondor and Rohan. Elessar is a royal title associated with his later reign. Neither is the alias by which the hobbits first know him at Bree.