diff --git a/ch04_keys.adoc b/ch04_keys.adoc
index 041e7ad7..890a0b7c 100644
--- a/ch04_keys.adoc
+++ b/ch04_keys.adoc
@@ -111,7 +111,7 @@ bitcoins it controls.
 ====
 
 The first and most important step in generating keys is to find a secure
-source of randomness (which computer scientists call _entropy_). Creating a Bitcoin key is almost
+source of randomness (which computer scientists ((("entropy")))call _entropy_). Creating a Bitcoin key is almost
 the same as "Pick a number between 1 and 2^256^." The exact method you
 use to pick that number does not matter as long as it is not predictable
 or repeatable. Bitcoin software uses cryptographically secure random