The play's title is abbreviated from its initial version: Et in Arcadia ego. Arcadia refers to the pastoral ideal; the phrase literally translates, "and in Arcadia I". The tradition of placing a tomb in a pastoral idyll can be traced to Vergil's Eclogues, while the phrase first appears in Poussin's 1637 painting. Both the image and the motto are commonly considered a memento mori, with the phrase being spoken by Death: "I, too, am in Arcadia". But the enigmatic phrase remains a subject of much academic discussion.
Lady Croom, enthusing about paintings of pretty landscapes, translates the phrase as "Here I am in Arcadia!" Thomasina drily comments, "Yes Mama, if you would have it so". Septimus notices; later, suspecting his pupil will appreciate the motto's true meaning, he offers the translation "Even in Arcadia, there am I". He is right – "Oh, phooey to Death!" she exclaims. Although these brief exchanges are the only direct references in the play to its title, they presage the two main characters' fates: Thomasina's early death, and Septimus's voluntary exile from life. Stoppard originally wanted to make this connection more explicit by using Et in Arcadia Ego for the title, but "box office sense prevailed".
In a more obvious sense, the title also invokes the ideal of nature as an ordered paradise, while the estate's landscape steadily evolves into a more irregular form. This provides a recurring image of the different ways in which "true nature" can be understood, and a homely parallel to Thomasina's theoretical description of the natural world's structure and entropic decline using mathematics.