:s/public_name/name/g

app/controllers/activities_controller.rb

 
     # Never trust parameters from the scary internet, only allow the white list through.
     def activity_params
-      params.require(:activity).permit(:public_name, :description, :location, :start, :end, :deadline)
+      params.require(:activity).permit(:name, :description, :location, :start, :end, :deadline)
     end
 end

app/models/activity.rb

 # An Activity represents a single continuous event that the members of a group may attend.
 # An Activity belongs to a group, and has many participants.
 class Activity < ApplicationRecord
-  # @!attribute public_name
+  # @!attribute name
   #   @return [String]
   #     a short name for the activity.
   #
     dependent: :destroy
   has_many :people, through: :participants
 
-  validates :public_name, presence: true
+  validates :name, presence: true
   validates :start, presence: true
   validate  :deadline_before_start, unless: "self.deadline.blank?"
   validate  :end_after_start,       unless: "self.end.blank?"

app/views/activities/_form.html.erb

 
   <div class="actions">
     <div class="form-group">
-      <%= f.label :public_name %>
-      <%= f.text_field :public_name, class: 'form-control' %>
+      <%= f.label :name %>
+      <%= f.text_field :name, class: 'form-control' %>
     </div>
     <div class="form-group">
       <div class="row">

app/views/activities/show.html.haml

   .col-md-9
     .panel.panel-default
       .panel-heading
-        = @activity.public_name
+        = @activity.name
         - if @activity.may_change?(current_person)
           = link_to edit_group_activity_path(@group, @activity), class: 'pull-right' do
             %i.fa.fa-pencil

app/views/groups/show.html.haml

               %tr
                 %td
                   = link_to group_activity_path(@group, a) do
-                    = a.public_name
+                    = a.name
                     = render partial: "activities/state_counts", locals: {counts: a.state_counts}
                 %td
                   = distance_of_time_in_words_to_now(a.start)
                 %tr{class: p.row_class, data: {activity_id: a.id, person_id: current_person.id}}
                   %td
                     = link_to group_activity_path(a.group, a) do
-                      = a.public_name
+                      = a.name
                   %td
                     = render partial: "activities/presence_buttons", locals: {activity: a, person: current_person, state: p.attending}
                   %td
                 %tr
                   %td
                     = link_to group_activity_path(a.group, a) do
-                      = a.public_name
+                      = a.name
                   %td
                   %td