diff --git a/addon/webextension/background/communication.js b/addon/webextension/background/communication.js
index 19a6e5bb69..d1c72ebca6 100644
--- a/addon/webextension/background/communication.js
+++ b/addon/webextension/background/communication.js
@@ -71,7 +71,7 @@ this.communication = (function() {
   }
 
 
-  // A singleton/sentinal (with a name):
+  // A singleton/sentinel (with a name):
   exports.NO_BOOTSTRAP = {name: "communication.NO_BOOTSTRAP"};
 
   return exports;
diff --git a/addon/webextension/onboarding/slides.js b/addon/webextension/onboarding/slides.js
index bc3124121a..e12bff4abc 100644
--- a/addon/webextension/onboarding/slides.js
+++ b/addon/webextension/onboarding/slides.js
@@ -84,30 +84,30 @@ this.slides = (function() {
     // termsAndPrivacyNoticeCloudServices is a more complicated substitution:
     let termsContainer = doc.querySelector(".onboarding-legal-notice");
     termsContainer.innerHTML = "";
-    let termsSentinal = "__TERMS__";
-    let privacySentinal = "__PRIVACY__";
-    let sentinalSplitter = "!!!";
+    let termsSentinel = "__TERMS__";
+    let privacySentinel = "__PRIVACY__";
+    let sentinelSplitter = "!!!";
     let linkTexts = {
-      [termsSentinal]: browser.i18n.getMessage("termsAndPrivacyNoticeTermsLink"),
-      [privacySentinal]: browser.i18n.getMessage("termsAndPrivacyNoticyPrivacyLink")
+      [termsSentinel]: browser.i18n.getMessage("termsAndPrivacyNoticeTermsLink"),
+      [privacySentinel]: browser.i18n.getMessage("termsAndPrivacyNoticyPrivacyLink")
     };
     let linkUrls = {
-      [termsSentinal]: "https://www.mozilla.org/about/legal/terms/services/",
-      [privacySentinal]: "https://www.mozilla.org/privacy/firefox-cloud/"
+      [termsSentinel]: "https://www.mozilla.org/about/legal/terms/services/",
+      [privacySentinel]: "https://www.mozilla.org/privacy/firefox-cloud/"
     };
     let text = browser.i18n.getMessage(
       "termsAndPrivacyNoticeCloudServices",
-      [sentinalSplitter + termsSentinal + sentinalSplitter,
-       sentinalSplitter + privacySentinal + sentinalSplitter]);
-    let parts = text.split(sentinalSplitter);
+      [sentinelSplitter + termsSentinel + sentinelSplitter,
+       sentinelSplitter + privacySentinel + sentinelSplitter]);
+    let parts = text.split(sentinelSplitter);
     for (let part of parts) {
       let el;
-      if (part === termsSentinal || part === privacySentinal) {
+      if (part === termsSentinel || part === privacySentinel) {
         el = doc.createElement("a");
         el.href = linkUrls[part];
         el.textContent = linkTexts[part];
         el.target = "_blank";
-        el.id = (part === termsSentinal) ? "terms" : "privacy";
+        el.id = (part === termsSentinel) ? "terms" : "privacy";
       } else {
         el = doc.createTextNode(part);
       }