form_helper_submit.rb

def submit(value = nil, options = {})
  # ...
  value ||= submit_default_value
  # ...
end

def submit_default_value
  object = convert_to_model(@object)
  key    = object ? (object.persisted? ? :update : :create) : :submit

  model = if object.respond_to?(:model_name)
    object.model_name.human
  else
    @object_name.to_s.humanize
  end

  defaults = []
  # Object is a model and it is not overwritten by as and scope option.
  if object.respond_to?(:model_name) && object_name.to_s == model.downcase
    defaults << :"helpers.submit.#{object.model_name.i18n_key}.#{key}"
  else
    defaults << :"helpers.submit.#{object_name}.#{key}"
  end
  defaults << :"helpers.submit.#{key}"
  defaults << "#{key.to_s.humanize} #{model}"

  I18n.t(defaults.shift, model: model, default: defaults)
end